Transcript ppt - Tufts University

COMP 150-IDS: Internet Scale Distributed Systems (Spring 2015)
A Very Brief History of
Early Digital Networking
Noah Mendelsohn
Tufts University
Email: [email protected]
Web: http://www.cs.tufts.edu/~noah
Copyright 2012 & 2015 – Noah Mendelsohn
Shannon
&
Information Theory
2
© 2010 Noah Mendelsohn
Claude Shannon and Information Theory
1948: Claude Shannon publishes: A mathematical theory of communication*
* http://cm.bell-labs.com/cm/ms/what/shannonday/shannon1948.pdf
3
Photo by Tekniska Museet
© 2010 Noah Mendelsohn
Claude Shannon and Information Theory
 Shannon’s work is as fundamental to digital communication as Turing’s
is to digital computing
 Information theory
– Quantifies information: how much information does a bit represent?
– Relates information transmission to bandwidth requirements
– Provides quantitative analysis of rate at which information can be sent over a noisy
channel
 Shannon showed that information could be communicated reliably
 He predicted how much information could be communicated reliably
given that channel characteristics are known
 BTW: Shannon and Turing knew each other and met for several months
4
© 2010 Noah Mendelsohn
Whirlwind, SAGE
&
US Air Defense
5
© 2010 Noah Mendelsohn
Early history of digital data transmission
 1948: Claude Shannon publishes: A mathematical theory of
communication*
 Late 1940’s: US seeks means of providing cold-war air defense
 Late 1949: Digital Radar Relay – experiment sending radar dataover phone
lines - first digital transmisison over the phone
 1951: MIT Whirlwind machine goes online
6
© 2010 Noah Mendelsohn
Whirlwind computer
7
© 2010 Noah Mendelsohn
Whirlwind computer
 The first significant real time computer system
 Innovation: core memory & digital networking
 5000 vacuum tubes
 16 bit parallel ALU
 20,000 instructions/second – limited by storage speed
 4000 bytes of core memory – invented for Whirlwind
Pictures by Dan Smity
8
© 2010 Noah Mendelsohn
Core Memory
Aside: for 20 years before transistor memories became available,
core memory made digital computing practical
9
© 2010 Noah Mendelsohn
Early history of digital data transmission
 1948: Claude Shannon publishes: A mathematical theory of
communication*
 Late 1940’s: US seeks means of providing cold-war air defense
 Late 1949: Digital Radar Relay – experiment sending radar dataover phone
lines - first digital transmisison over the phone
 1951: MIT Whirlwind machine goes online (approximate)
 1953: Cape Cod System tests sending radar data through phone lines to
Whirlwind
10
© 2010 Noah Mendelsohn
Forrester promptly began preparing to receive and process digitized
radar signals. The feasibility demonstration of the radar/digital-data
concept took place at Hanscom Field in September 1950. The radar,
which was an original experimental model of a microwave earlywarning unit built by the wartime MIT Radiation Laboratory, closely
resembled the radars used in the D-Day invasion of Normandy.
History of Whirlwind and MIT Lincoln Lab: http://www.ll.mit.edu/about/History/origins.html
11
© 2010 Noah Mendelsohn
Forrester promptly began preparing to receive and process digitized
radar signals. The feasibility demonstration of the radar/digital-data
concept took place at Hanscom Field in September 1950. The radar,
which was an original experimental model of a microwave earlywarning unit built by the wartime MIT Radiation Laboratory, closely
resembled the radars used in the D-Day invasion of Normandy.
While military observers watched closely, an aircraft flew past the
radar, the digital radar relay transmitted the signal from the radar to
Whirlwind via a telephone line, and the result appeared on the
computer's monitor. The demonstration was a complete success and
proved the feasibility of ADSEC's air defense concept.
History of Whirlwind and MIT Lincoln Lab: http://www.ll.mit.edu/about/History/origins.html
12
© 2010 Noah Mendelsohn
Early history of digital data transmission
 1948: Claude Shannon publishes: A mathematical theory of
communication*
 Late 1940’s: US seeks means of providing cold-war air defense
 Late 1949: Digital Radar Relay – experiment sending radar dataover phone
lines - first digital transmisison over the phone
 1951: MIT Whirlwind machine goes online (approximate)
 1953: Cape Cod System tests sending radar data through phone lines to
Whirlwind
 1957: First SAGE system, based on Whirlwind technology – SAGE runs US
air defenses until 1983! (video) * *
Good book on Whirlwind: Bright Boys, by Tom Green
History of Whirlwind and MIT Lincoln Lab: http://www.ll.mit.edu/about/History/origins.html
13
© 2010 Noah Mendelsohn
The SAGE Computer System (AN/FSQ-7)
 60,000 vacuum tubes[8] (49,000 in the computers)
 Consumed up to 3 megawatts of electricity
 Performed about 75,000 instructions per second
 Memory: ~65,000 32 bit words
Source: http://en.wikipedia.org/wiki/AN/FSQ-7_Combat_Direction_Central
14
© 2010 Noah Mendelsohn
Paul Barran
&
Packet Switching
15
© 2010 Noah Mendelsohn
Paul Baran, Donald Davies and Packet Switching
 1964: Paul Baran proposes packet switching design
 Design goal: a resilient network to maintain command and control
16
© 2010 Noah Mendelsohn
Circuit switching (the way the old phone system worked)
When you make a call…
…switches are set to reserve links
for a fixed route for the life of the call
17
© 2010 Noah Mendelsohn
Packet switching
When you communicate…
…packets find independent routes
through the network
18
© 2010 Noah Mendelsohn
Packet switching
When you communicate…
…packets find independent routes
through the network
19
© 2010 Noah Mendelsohn
Paul Baran, Donald Davies and Packet Switching
 1964: Paul Baran proposes packet switching design
 Design goal: a resilient network to maintain command and control
 Questions to consider:
– Performance: better or worse than circuit switch?
– How are routing tables maintained?
– Why was it counter-intuitive
 Success of early packet switching tests motivates government funding
for ARPANet
20
© 2010 Noah Mendelsohn
Packet vs. Circuit Switching
 Circuit switching
– Good for continuous predictable flows
– Easy to put “smarts” into the middle of the network (smart switches)
– The way to go when all you have is analog communication
 Packet switching
– Adapts well to changing loads
– Relatively cheap to make lots of quick “connections”
– Paul Baran’s insight: digital makes packet switching possible (packet does not
“degrade” as it gets copied through intermediate nodes)
 1960’s: AT&T did not believe packet switching would work
 Packet switching tends to put value outside the network
 When systems are fault-tolerant, you can often build them from cheaper
components
21
© 2010 Noah Mendelsohn
A Brief History of The Internet
22
© 2010 Noah Mendelsohn
History of the Internet
DNS
(Mockapetris)
Baran &
Davies
Packet
Switching
Work
Prompts
Gov’t
Investment
14 Arpanet
Nodes +
1/month
NSFNet
1989:
80,000
hosts
Tim BL
Proposes
Web
ARPANet
Developed
1960
Bob
Metcalfe
Begins
Ethernet
work at
Xerox PARC
First Web
Server
1965
1970
TCP/IP
(Cerf & Kahn)
1975
1980
1985
1990
Adapted from http://www.computerhistory.org/internet_history/
23
© 2010 Noah Mendelsohn
History of the Internet
DNS
(Mockapetris)
Baran &
Davies
Packet
Switching
Work
Prompts
Gov’t
Investment
14 Arpanet
Nodes +
1/month
24
NSFNet
Metcalfe
Begins
Ethernet
work at
By 1992, the Internet
is doubling
Xerox PARC
1989:
80,000
hosts
Tim BL
Proposes
Web
in size every 3 months
ARPANet
Developed
1960
First Web
Server
1965
1970
TCP/IP
(Cerf & Kahn)
1975
1980
1985
1990
© 2010 Noah Mendelsohn